The goal of this project is to study the role of central oxytocin pathways in the mediation of social attachment. This project uses molecular, cellular, and behavioral techniques with a focus on monogamous mammals. This research has focused primarily on rodents, comparing monogamous and non-monogamous species as well as developing transgenic mice. The major finding is that the oxytocin receptor appears to be distributed in markedly different patterns across species, leading to different functional effects of the peptide. In the monogamous prairie vole, oxytocin has an important role for pair bonding. The species differences in receptor distribution are not associated with variations in the coding sequence of the receptor gene but may be due to extensive variation in the promoter. Recently, anatomic and molecular studies in monkeys have been undertaken prior to investigating the human brain. Mapping studies in rhesus monkey have identified an oxytocin receptor in the u terus but fail to detect this receptor in brain using either binding techniques or polymerase chain reaction. A related receptor, the V1a receptor, has been found in select regions of the rhesus forebrain with binding and in situ hybridization and, based on its pattern of expression, may have an important role in memory. The ultimate purpose of this research is to identify the neural circuitry for attachment behavior, providing a potential map of areas for study in human disorders of social attachment, such as autism.